It is known to make pressure-sensitive surfaces by instrumenting a mat or other structure which includes a surface region with an array of pressure sensing elements. For example, an array of pressure sensors of the type described in PCT publication No. WO 99/04234 (Reimer, et al.), can be used to detect the location and pressure applied by several simultaneous points of contact.
The surface may be covered with a membrane as described, for example, in WO 00/73982 (Inkster). Such membranes can cause problems, however. A membrane can distribute pressure so that touching at one location causes signals from the pressure sensors in a surrounding area. The prior pressure-sensitive surfaces described above provide no way to isolate the response of a set of pressure sensors from neighboring ones.
In conventional pressure-sensitive structures which include a membrane overlying an array of pressure sensors, the membrane distributes pressure imposed by an indentor radially outwardly from the indentor in a generally uniform manner. The inventors have determined that by selecting the properties of a membrane, it is possible to control how force from an indentor will be distributed over pressure sensors in a pressure-sensitive structure. This can be very beneficial in some applications.